I was born in Chicago and grew up in Grand Rapids Michigan USA where I attended Calvin College. I spent a year as an agricultural volunteer in Nigeria, West Africa before continuing my education with an MS in Biology from Central Michigan University and a PhD in Forest Ecology from Purdue University, After completing my PhD in 1993, I took a position at Stephen F. Austin state University (SFASU) in the east Texas Pineywoods. I teach both undergraduate and graduate courses in areas including general biology, botany, local flora, plant systematics, plant ecology, and wetland ecology. My research interests include description and analysis of the natural vegetation and ecosystems of the Texas Pineywoods and the West Gulf Coastal Plain (USA) the impact of invasive species such as giant salvinia on local wetland ecosystems, changes over time in permanent plots in local forest ecosystems, and floristic botany. In addition I curate the Biology Department's ASTC herbarium and maintain the 'Pineywoods Plants Digital gallery' (a pictorial documentation of the local east Texas flora) along with several other related galleries. My research can be broadly summed up as "What grows in the woods and why". I am actively recruiting graduate students. If you are interested in joining my lab please contact me and apply with the Graduate School (www.sfasu.edu/graduate/) at Stephen F. Austin State University.

14

Graduate Theses Directed

50

Conference Presentations

21

Research Publications

12

Grants Received

Biology 121: Concepts of Biology

Core curriculum Biology course for non-majors (4 hours)

An introduction to the biological sciences

Description

Humans are biological organisms and we interact with other organisms on a daily basis. Moreover, the ecological future of the earth may depend on decisions made by humans from our generation. For these reasons, a basic knowledge of life-processes and an awareness of the biological world is a vital part of any education regardless of what profession one is preparing for. This course introduces you the central concepts of modern biology: the Cell Theory, the Central Dogma, the Theory of Evolution, and the Concept of Ecosystems. Along the way you will discover many of the sub-disciplines of biology including cell and molecular biology, genetics, botany, zoology, physiology, and ecology. The course includes four lecture tests worth approximately 17% of the course grade each and a laboratory section worth 33 % of the grade. The course is aimed at non-Biology majors and is attended to provide a well-rounded introduction to the biological sciences. Current students should refer to the D2L page for this course to find the syllabus, course notes, and other resources.

Students who successfully complete Concepts of Biology will be able to:

Biology 131 (231): Introduction to Botany

Description

As living organisms, humans depend on the plant world to provide us with food, energy, wood, fiber and to sustain the rich web of life on our earth. Today, with increasing human pressure on earth's ecosystems, the ecological future of the earth may depend on decisions made by humans from our generation. For these reasons, a basic knowledge of life-processes and an awareness of the plant world is a vital part of education regardless of what profession one is preparing for. This course introduces students to basic biological concepts and will exposes them to several of the sub-disciplines of botany: cell biology, plant anatomy, plant physiology, biodiversity, and ecology. The course includes four lecture tests worth approximately 17% of the course grade each and a laboratory section worth 33 % of the grade. While open to non-majors, The course is aimed at Biology majors and is attended to provide foundation for continued studies in the biological sciences. Current students should refer to the D2L page for this course to find the syllabus, course notes, and other resources.

Students who successfully complete Botany will be able to:

Understand the structure and functions of plant cells, organelles, tissues, and tissue systems.

Understand the structure and function of plant roots, stems, and leaves.

Understand the principles of photosynthesis, including a knowledge of energy molecules (ATP and NADPH); the light reactions including its products and byproducts; the Calvin Cycle and its products; the relationship between the light reactions and Calvin Cycle; and C4 and CAM photosynthesis.

Understand basic plant reproduction, including the concepts of life cycles, alternation of generations, gametangia, sporangia, and specialized reproductive features.

Understand the evolution and diversity of the major groups of land plants including bryophytes, lycophytes, ferns, gymnosperms, and angiosperms.

Have a basic knowledge of ecosystems, communities, succession, interactions between plants, other organisms and their environment.

Biology 225: Local Flora and Fauna

Introduction to the native and naturalized plants of the Texas pIneywoods and their habitats ('Flora' version of Biology 225).

Description

Course Description: This course introduces students to the native and naturalized plants of the east Texas Pineywoods and to the habitats in which they grow. It satisfies core curriculum requirements for non-Biology majors as well as providing credit for biology majors. Knowledge of the natural plants and the vegetation around us provides an excellent way to appreciate the natural world. Plant identification skills are also vital to many other botanical and biological fields. Plant ecology is the study of the interactions of plants with each other and their environment. Wildlife studies, wetland studies, and resource management, and ecology all require the ability to know local plant species. There is a demand for individuals with knowledge of vegetation and good plant identification skills. For example, most National Forests and Natural Resource agencies hire a field botanist. Wetland delineation, a skill needed by many private environmental consulting firms, involves being able to identify wetland plants. This course provides the basic skills necessary to start identifying plants, enable you to recognizes many species ‘on sight’ and will introduce you to the various natural habitat types of the East Texas Pineywoods and the plant species that characterize them. The course will also introduces some of the terminology scientists use to identify plants. Students also become familiar with the major vascular plant groups and their evolutionary relationships. Other versions of this course taught by other faculty focus on fauna such insects, birds, or other vertebrates. Current students should refer to the D2L page for this course to find the syllabus, course notes, and other resources.

Biology 403/503: Terrestrial Plant Ecology

An upper division or graduate course in plant ecology (3 hours).

An introduction to community ecology, community data analysis, autecology, and ecological systems.

Description

Plant Ecology is the study of how plants relate to each other and to their environment. In addition to basic research, plant ecologists also study the effects of land management on plant populations and vegetation thereby playing a critical role in dealing with today's environmental problems. Along with discussing basic ecological concepts, this course will introduce you to methodology used to sample and analyze vegetation. There are 2 lecture tests and a final examination along with a series of laboratory assignments. Graduate students also complete an independent research project. Current students should refer to the D2L page for this course to find the syllabus, course notes, and other resources.

Biology 435/535: Plant Systematics

Description

Plant Taxonomy or Systematic Botany is the science of identifying, naming, and classifying plants. This course consists of a closely-integrated concurrent laboratory and lecture section. It introduces students to the classification, naming, diversity and phylogeny (evolutionary-descent patterns) of plants. Students are also exposed to the principal natural habitat types of the east Texas Pineywoods and the vascular plant species that characterize them. Weekly field trips enable students to learn to identify approximately 120 local native and naturalized species on sight. Two lecture tests, a final, a series of laboratory exercises and quizzes comprise the course grade. Graduate students also collect and prepare a series of herbarium specimens. Current students should refer to the D2L page for this course to find the syllabus, course notes, and other resources.

Course topics and activities include:

Principals of scientific botanical nomenclature.

The herbarium and its role as a resource for education and research in plant systematics and ecology.

Modern perspectives on plant classification and current theories regarding phylogenetic relationships among the land plants.

Current methods used to investigate phylogenetic relationships among plants.

Biology 503: Aquatic Vascular Plants

Description

Wetlands form the transition between terrestrial and aquatic ecosystems and provide critical resources for waterfowl, fish, and other wildlife. They also provide important natural services including natural flood control, recreation, and water purification. Although historically maligned and ignored, recent ecological awareness has revealed the importance of wetlands. The ability to recognize wetland plants is important not only for scientific reasons but also for legal ones. Delineation of wetlands is an important part of land use planning as owners, managers, and developers seek to comply with wetland protection laws. This course is largely a laboratory course that emphasizes identification of aquatic and wetland plants. You will learn to identify roughly150 species and will see a wide range of East Texas wetland and aquatic ecosystems. You will also learn what sources (books, keys) to turn to when identifying an unknown wetland plant in East Texas. In addition, we will discuss topics relating to the ecology and management of wetland plants. Current students should refer to the D2L page for this course to find the syllabus, course notes, and other resources.

Course topics and activities include:

Weekly excursions foccusing on observing and identifying wetland plants in their natural habitat.

Biology 470: Seminar in Biology

Description

The ability to organize and publicly present one's findings in a brief, informative presentation is an essential skill for scientists and professionals. Biology 470 provides upper-level Biology majors with experience preparing and presenting a seminar on a specific topic. Students also take the Major Fields test as a part of the Biology Department's assessment program. Multiple professors teach this course, each with different themes. My section-topics are either plant ecology and plant geography or the impact of non-native invasive species on natural ecosystems. The theme of the most recent section (Spring 2018) is the impact of invasive species. Each student chooses a non-native invasive species (not restricted to those impacting North America!) and prepares a literature review-based presentation that addresses current research relating to topics including the species' ecological role in its native range, its impact where it is invasive, and control measures. The invasive species may be a plant, animal or other organism that impacts natural ecosystems. Current students should refer to the D2L page for this course to find the the syllabus, course notes, and other resources.

The Western Woods: Forest Ecosystems of Eastern Texas and Adjacent Louisiana

Description of Local vegetation with a pictoral guide to the indicator species for each ecosystem type. 2017-Present.

A book summarizing vegetation ecology research in the Texas and Louisiana

Abstract

The “Great Western Woods” forms the western edge of the warm humid forest region of southeastern North America. Moving to the west, the climate dries markedly giving rise to the prairies, savannas, and ranch-lands of central Texas and the arid grasslands and deserts beyond. The Western Woods is part of the vast pine and mixed forest region of America’s “Deep South” covering the Atlantic coastal and the coastal plain of the Gulf of Mexico. It occurs on the Gulf coastal plains of Louisiana and Texas, an area often called the West Gulf Coastal Plain. Within the West Gulf Coastal Plain, the forests of east Texas are known as the Pineywoods -a term that may also include adjacent parts of Louisiana. This on-going project involves writing a book summarizing more than 20 years of my vegetation ecology research in the region. The manuscript currently stands at 70 pages of pure text in 10 chapters along with 45 figures and tables and a collection of photographs representing indicator species for each local ecosystem type. The work is largely based on multivariate analysis of a field data set of 680 plots complied from sixteen separate datasets collected in the course of prior research projects. The figure (below) shows an ordination diagram and a classification of the samples into vegetation types based on their species composition.

Figure: A detrended correspondence analysis of 680 vegetation sample plots combining overstory, midstory and ground layer vegetation from the West Gulf Coastal Plain of Texas and Louisiana. Polygons and symbol/color-codes represent a classification into ecosystem types based on TWINSPAN and flexible-Beta cluster analyses. The direction and length of the red lines represents the respective direction and strength of correlations with environmental factors.

The Wetland Vegetation of Caddo Lake

Six natural wetland vegetation types were described and mapped for the wetlands associated with Caddo Lake, Texas.

Description

An old project completed in the 1990's, the resulting descriptions and map (below) of six vegetation types for the baldcypress swamp ecosystem at Caddo Lake yielded a publication and formed the basis for an on-going long term permanent-plot study documenting vegetation changes, some associated with growing populations of non-native invasive species. The work was funded by a grant from the US National Biological Service.

Twenty Years of Vegetation Change at Caddo Lake, Texas

Long-Term Vegetation Monitoring: 1994-Present

56 GPS-marked plots were revisited six times between 1995 and 2014 in order to observe vegetation.

Abstract

Caddo Lake, on the Texas-Louisiana USA border, includes extensive Taxodium distichum swamps and is an internationally important wetland under the Ramsar Convention. In 1995 we described wetland plant communities along a hydrological gradient. In 2005 we established GPS points marking 56 1000m2 permanent plots at the 1995 locations and re-sampled them in 2005, 2009, 2011, 2012, and 2014. 1995 non-woody vegetation was largely dominated by native species with Eichhornia crassipes restricted to a limited area. By 2005 Eichhornia was abundant and Alternanthera philoxeroides and Hydrilla verticillata, had also increased. By 2009, Salvinia molesta had appeared (likely first in 2007) and become widespread while Eichhornia remained abundant. During 2011, a severe drought year with low water levels, Salvinia and ichhorniaE declined in abundance but were still widely distributed spatially. Salvinia recovered strongly in 2012, apparently at the expense of Eichhornia which did not regain former abundances. By 2014, marked declines were observed in several formerly abundant native species including Wolfia columbiana, Spirodella polyrrhiza, Nuphar lutea,and Nelumbo luteum while Salvinia and Alternanthera remained abundant. Non-natives Hygrophylla polysperma and Najas minor also appeared during the study. These changes were reflected in canonical correspondence analysis results where plots for each period occupied largely different regions in ordination space. The ordination showed relationships not only between vegetation and the underlying hydrologic gradient but also with the sample-year and annual water levels. Several novel communities appeared during the study including floating mats dominated by Salvinia and Oxycaryum cubense (after 2009) and mats of A. phioxeroiodes, S. molesta, and the formerly uncommon native Hydrocotle ranunculoides (mainly in 2014). The events at Caddo Lake are an unplanned 'experiment' in community re-organization following introduction of multiple invasive species. Marked year-to-year differences in vegetation continue to be observed; relationships between invasive species and native species have not yet stabilized as evidenced by marked 2012-to-2014) declines in formerly-abundant native species. Continued monitoring will enable us to observe longterm outcomes and may contribute to data that enhance our general understanding of biogeographic changes associated with species invasions.

This on-going project has generated three MS theses, a proccedings publication, and numerous conference presentations. The most recent poster, presented at an international meeting in 2015 is shown below.

An Ecological Classification System for the West Gulf Coastal Plain

Land classification on basis of natural vegetation, soils, and topography 1994-2009

462 sample plots were used to describe ecological land units and develop a field guide.

Abstract

We developed a multifactor ecological classification system (ECS) for the National Forests and adjacent lands of Texas and Louisiana. The ECS classifies lands into ecosystem types: repeating combinations of potential natural vegetation, soils, and physiography. Mature forest stands were sampled across a range of soil and topographic situations. 11 separate data sets with a representing 18 landtype associations (geographic regions with similar geology) withing the west Gulf coastal plain were sampled over an eight-year period (1994-2002). Overall we sampled a total of 462 sites sampled and encountered 956 species. Non-metric multidimensional scaling ordinations and TWINSPAN classification of the samples based on ground-layer vegetation corresponded to gradients of topographic position, fire frequency, disturbance, hydrology and soil nutrients. Ordination and classification results formed the basis for a final classification of the sample stands and for descriptions and dichotomous keys for seven 'landtype phases' (local ecosystem types) that share soil and topographic attributes, natural plant communities, and responses to management or disturbance. A total of 137 landtype phases across 18 landtype associations were described and are presented in an ECS field guide.

ECS provides an ecologically relevant way to stratify the landscape for inventory, conservation, research, or management and gives the Forest Service and other professionals a valuable tool to aid ecologically-informed decisions. The project generated a field guide, three publications, three MS theses and was supported by grants from the USDA Forest Service and the Nature Conservancy.

Dehnisch, M.S. 1998. A comparison of five common ordination methods using the vegetative communities of the Winn and Catahoula ranger districts of the Kisatchie National Forest. M.S. Thesis. Stephen F. Austin State University. Nacogdoches, TX.

Vegetation Community Changes in Two National Forests in the Pineywoods, East Texas

M.S. Thesis of Trisha L. Williams 2015-2017

Thirty upland and mesic stands were re-sampled after 20 years and vegetation changes observed

Abstract

Despite extensive research into forest succession, little research has been directed to long-term studies. The objective of this research was to characterize vegetation changes that occurred over a 20 year period in upland and mesic forests. Thirty upland forest stands that were previously sampled in 1995 and 1996 when developing an ecological classification system for the region were re-sampled. None of the selected stands had experienced dramatic disturbance during the study period. This research provided several results: 1) More vegetation compositional change occurred in the longleaf pine, dry-mesic and mesic ecosystem types than in forested seeps and dry sandy uplands; 2) Changes in the midstory stratum were greater than those in the ground layer and the overstory changed the least. In particular, midstory flowering dogwood (Cornus florida) declined markedly. 3) Ground-layer species richness was somewhat lower in 2016 than in 1995 although differences could have resulted from inconsistency in sampling-intensity when looking for rare off-plot species. This study is part of a growing body of research on long-term studies relating to forest succession and can serve as a benchmark for future research in the region.

M.S. Thesis:

Williams, Trisha L. 2016. Vegetation Community Changes in Two National Forests in the Pineywoods, East Texas. M.S. Thesis. Stephen F. Austin State University. Nacogdoches, TX.

Procrustes analysis to show vegetation changes in sample plots from 1995-2016:

Arbuscular Mycorrhizal Communities in East Texas Forest Ecosystems

Molecular methods were used to detect AMF communities associated with the roots of common east Texas forest understory species.

Description

Arbuscular mycorrhizal fungi (AMF), Phylum Glomeromycota, form a symbiosis with the roots of a majority of terrestrial plant species thereby enhancing root absorption. AMF from east Texas forests were studied by sampling roots from three widely-occurring native host plants: Callicarpa americana, Chasmanthium sessiliflorum, and Toxicodendron radicans. Root samples from the three host species were taken from a a range of habitats. Denaturing Gradient Gel Electrophoresis (DGGE) and massive parallel sequencing analysis were used to identify all taxonomic units of fungi present in each sample. Results indicated that many Arbuscular mycorrhizal fungal taxa showed preference for certain host plants. Arbuscular mycorrhizal fungal communities on the same host species also differed across different plant community-soil-topography combinations. They also changed seasonally with the chief difference being between wet and dry periods rather than temperature or season. The study has thus far yielded two publications and three Biotechnology M.S. theses directed by Dr. Alexandra Martynova-Van Kley.